According to the BACnet protocol documentation:

Defines a standardized object whose properties represent the externally visible characteristics of a value that is sampled periodically over a specified time interval. The Averaging object records the minimum, maximum and average value over the interval, and makes these values visible as properties of the Averaging object. The sampled value may be the value of any BOOLEAN, INTEGER, Unsigned, Enumerated or REAL property value of any object within the BACnet device in which the object resides. Optionally, the object property to be sampled may exist in a different BACnet device. The Averaging object shall use a "sliding window" technique that maintains a buffer of N samples distributed over the specified interval. Every (time interval/N) seconds a new sample is recorded displacing the oldest sample from the buffer. At this time, the minimum, maximum and average are recalculated. The buffer shall maintain an indication for each sample that permits the average calculation and minimum/maximum algorithm to determine the number of valid samples in the buffer.

Objects of type averaging have the following properties:

•attemptedSamples

•averageValue

•description

•maximumValue

•maximumValueTimestamp

•minimumValue

•minimumValueTimestamp

•objectIdentifier

•objectName

•objectPropertyReference

•objectType

•profileLocation

•profileName

•propertyList

•tags

•validSamples

•varianceValue

•windowInterval

•windowSamples